Herald and tribune. [volume] (Jonesborough, Tenn.) 1869-current, 1887-04-21
SCIENTIFIC

of Rome is said to be the largest in
the world, weighing about sixty-three
tons. 1t was made Of fluid compressed
steel.
A recently perfected gauge for scrib-
ing around circles or on coneave edges
for timers S is unsurpassed, as it
takes the place of dividers and is far
more accurate.
In New York 1000 horse hides and
10000 sheep skins are now used yearly
to cover b~aseballs. A horse hide covers
twelve dozen baseballs and a sheep
skin three dozen.
A manufacturer in France has just
made a wire rope over three miles long,
weighing sixteen tons. 1t is 224 inches
in circumference, and has a breaking
strain of t~hirty-nine tons.
The discharge of water from steam
jackets of compound engines seldom
amounts, where the jackets are efficient,
to less than three pounds per indicated
horse power per hour.
Cast steel is steel that has been
melted in a "pot" and poured into a
"mould," thus becoming an "ingot,"
which is after hammered or rolled into
the size required. 1t may be of various
"tempers," varying in percentage of
carbon, which they contain from three
quarters or less to IL or more.
The oldestiron-ore mine in the United
States that is 10Y in operation is the
Iron Hill Mine in Delaware, whichwas
discovered as early as 1854, and soon
afterwards opened. Ore is still taken
from this mine and used in Principle
Furnace, Maryland, the first stack for
which furnace was built in 1923.
1t is said that with a rock salt lens
photographs may be taken of a heated
object with a specially prepared plate)
in the dark. For instance. . photograph
could be made of a black-hot casting or
stove in dark room. This is because
it allows artificial light to pass through
it freely, while glass absorbs both
artificial heat and light.
The eyestone is really the front door
of a sea snail found on the South
American coast. Thousands of people
believe that these bits of shell are alive,
from the fact that they move when
placed in vinegar. The philosophical
explanation of the movement is that
the acid, acting upon the substance of
the shell, generates little bubbles of
gas which force it along through. the
iuid When you pick out an eyestone
De sure TO get one with grooves on the
fat side. Those that are smooth all
over are taken from the crayfish, but
are no good.
Berlin papers copy from the Ger
mania an account Of an important
discovery in glass manufacture made
by Friencrich Siemens, of Dresden. He
has succeeded in casting glass in thu
same way as metal is cast, and obtain
ing an article corresponding to cast
metal. This cast glass is hard, no
dearer in production than cast iron
and has the advantage of transparency
so that all flaws al be detected befor
it is 'applied to practicle use. 1t will b
much less exposed to injury iron
atmospheric influence than iron. TIL
process of production is not difficult
the chief feature being rapid cooling
The hardness and resisting power o
this cast glass are so great that expert
ments are being just now carried on
at the Siemens Glass Foundry a
Dresden with the purpose of ascertain
ing whether the material could be EN-
ployed for rails on railways.
Education Of the II uman Eye.
The following story from the Penn
Monthly is related to Agassiz, and 1t il
sufficiently characteristic Of this re
markably accurate observer to hav,
the merit Of probability. We are toll
that once upon a time the professo
had occasion to select an assistan
from one of his classes. There were
number Of candidates for the post c
honor, and finding himself in a quar-
Diary as to which one he should choos
the happy thought occurred to him {
subjecting three of the more promisin
students in turn to the simple test
describing the view from his laboratol
window, which overlooked the sit
yard Of the college. One said that ]
saw merely q broad fence and a brit
!, pavement; another added a stream
; soapy water; a third detected Il
: color of paint on the fence, noted
) green mould or fungus on the bricl
| and evidences Of "blueing" in t
water, besides other details, 1t is nee
|, less to tell which candidate was award
the coveted position,
|. Houdin, the celebrated prestigiat
: attributed his success in his protest.
mainly to his quickness of perceptiC
which, he tells us in his entertaini
autobiography, he acquired by educ
ing his eyes to detect n large numt
of objects at a single glance. His 81
pie plan was to select a shop wind,
full Of q miscellaneous assortment
articles, and walk rapidly past it
number Of times every day, writ
down each object which impressed
self on his mind. In this way he W
able, after a time, to detect instan.
neously all Of the articles in the W
dow, even though they might be nu
, bered by scores.
-~tS-..-
A Railway Tie Nursery.
49,